Component for a machine or industrial plant and method for controlling a component in a machine or industrial plant

ABSTRACT

A component is disclosed having a network communication device that controls transmission of data in a data network between the component and another component, without a repeat transmission of time-critical data of the plurality of data packets being possible in a transmission cycle. The network communication device is configured to (i) tolerate a possible packet error in a data packet received in a preceding transmission cycle, (ii) signal to the other component in a following transmission cycle a presence or absence of a packet error, (iii) determine whether the other component has signaled a presence of a packet error in a data packet sent by the component in the preceding transmission cycle, and (iv) depending on whether the other component signaled the presence of a packet error, adjust a number of redundancy data items in a data packet to be sent in the following transmission cycle.

This application claims priority under 35 U.S.C. § 119 to applicationno. DE 10 2017 215 100.5, filed on Aug. 30, 2017 in Germany, thedisclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a component for a machine orindustrial plant and a method for controlling a component in a machineor industrial plant, in both of which in the case of a data transferbetween the components of the industrial plant without data packetrepetition successive data packet errors are avoided, so that a secure,real-time-enabled data transfer is possible.

BACKGROUND

In an industrial plant, control devices are used for example forcontrolling transport systems, for controlling tools, such as weldingtools, screwing and/or drilling tools, riveting tools, etc., forcontrolling sensors, controlling actuators, such as linear motors androtary machines, etc. Normally, actions or tasks and thus the control ofa component of the industrial plant to be controlled, such as a tool,are dependent on actions or results of another component of theindustrial plant. Therefore, there is often a requirement that a datatransmission takes place in real time between the control device and thecomponents of the industrial plant to be controlled. In accordance withthe DIN 44300 standard (Information Processing), part 9 (Processingsequences) now superseded by DIN ISO/IEC 2382, the real-time operationof a computing system is understood to mean one in which programs forprocessing incoming data are constantly operationally ready, such thatthe processing results are available within a specified time interval.Depending on the specific application case the data can accrue accordingto a temporally random distribution or at predetermined times.

In real-time capable networks, the transmission of time-critical datapackets must be guaranteed within a specific time frame. In manyreal-time systems, this time window is defined by communication cycles,in which data are exchanged periodically or cyclically.

The reception of data packets must generally not be delayed beyond thistime window. In the real-time capable networks it is therefore ensuredthat valid control data and status information are available at specifictimes and can be further processed.

In industrial automation as an example of real-time capable networks,control and status data are continuously exchanged between a centralcontrol device and a plurality of sensors or actuators. In this case theimportant criteria are real-time capability with guaranteed maximumtransmission times and a high reliability of the data. As a result, thedata transmission procedure must ensure that data are successfullydelivered at a particular time.

A serious problem, however, is that in many real-time enabled networksthe available transmission capacity is not fully exploited by only onesingle time-critical service. The rest of the transmission capacity canbe used, among other things, for a transmission of additional,non-time-critical data to the same network node and/or a transmission oftime-critical and non-time-critical data to other network nodes in thesame transmission medium and/or transmission pauses to reduce the energyconsumption. The time frame and the allocation of the transmissioncapacity are usually performed by a central controller.

In the current transmission methods, such as Sercos III, EtherCAT,Profinet, etc., data packet transmission errors cannot be completelyeliminated. Depending on the transmission medium, such as unshieldedcable or wireless transmission, and possibly shortened data transmissioncycle times, one or more packet errors can occur in succession. Thiscannot be handled with the currently available error correctiontechniques, so that in the worst case the packet errors can lead to thefailure of at least one component of the industrial plant or even theentire industrial plant. As a result, costly downtimes of the industrialplant are incurred.

SUMMARY

The object of the present disclosure is to provide a component for amachine or industrial plant and a method for controlling a component ina machine or industrial plant, with which the above problems can besolved. In particular, a component for a machine or industrial plant anda method for controlling a component in a machine or industrial plantwill be provided, with which failures of components of the industrialplant can be minimized.

This object is achieved by a component for a machine or industrial plantaccording to the disclosure. The controller comprises a networkcommunication device for controlling a transmission of data in a datanetwork of the machine or industrial plant, in which data packets with apredetermined packet length are transmitted cyclically between thecomponent and at least one other component of the machine or theindustrial plant without a repeat transmission of time-critical data ofthe data packet being possible in a transmission cycle, wherein thenetwork communication device is designed to tolerate a possible packeterror in a received data packet, which was sent in the precedingtransmission cycle, and to signal to the at least one additionalcomponent in the following transmission cycle a presence or absence of apacket error, wherein the network communication device is configured todetermine whether or not the at least one other component has signaled apacket error for a data packet sent by the component in the previoustransmission cycle, wherein the network communication device isdesigned, depending on the determined result, to adjust the number ofredundancy data items in the data packet to be sent in the followingtransmission cycle, which will increase a correction probability of biterrors in the time-critical data to be sent.

With the component the security of the transmission quality isguaranteed by the fact that although error correction and errordetection are applied, not all packet errors can be explicitly avoided,but only critical multiple errors. Using this approach, the followingadvantages can be achieved at the same time.

With the described component very short data transmission cycle timesare possible, since no retransmissions are necessary. In particular,very short data transmission cycle times of this kind are less than orequal to 1 ms.

In addition, with the described component a moderate redundancy averagedover time for error correction is possible, because the redundancy onlyneeds to be increased in the rare cases when packet errors haveoccurred.

In addition, the component offers a high energy efficiency, since theadditional redundancy must only be transmitted and evaluated in rarecases.

In addition, the described component implements an efficient preventionof critical multiple errors, which in certain applications, e.g. in thearea of industrial communication in the industrial plant, represent thecrucial quality characteristic.

As a result, the component is also applicable in future, real-timeenabled networks with short cycle times that use a faulty transmissionmedium with an increased bit error probability, such as a radiotransmission, unshielded cables, etc., and in which a repeatedtransmission in a cycle is not possible and therefore is not an optionfor handling packet transmission errors.

Advantageous further embodiments of the component are specified in thedisclosure.

The network communications device may be configured, if no packet erroris determined in the preceding transmission cycle, to increase thenumber of time-critical data in the data packet to be transmitted in thefollowing transmission cycle or to include non-time-critical data, whichare indeed to be transferred but for which a time delay is non-critical,and wherein the network communication device is designed, if a packeterror is determined in the preceding transmission cycle, to include theredundancy data in the data packet to be sent in the followingtransmission cycle instead of the non-time-critical data or a portion ofthe time-critical data.

In a specific design the network communication device is also configuredto include in the data packet: a first piece of information concerningwhether a data packet, which in the preceding cycle was sent to thecomponent by the at least one additional component, had a packet erroror not, and a second piece of information concerning the currentconfiguration of the data packet to be sent in the current transmissioncycle, wherein the second information item can be used by the at leastone other component for an error correction of the time-critical data.The first information can be contained in one bit, and the second pieceof information can specify the number of check bits in the data packet.Additionally or alternatively, the redundancy data items are check bits.

It is conceivable that the network communication device is additionallydesigned to examine the time-critical data for bit errors and if atleast one bit error is present to perform an error correction of thetime-critical data on the basis of the second piece of information andthe redundancy data.

In one exemplary embodiment the component also has an application whichis designed to use the time-critical data, wherein the networkcommunication device is also designed to transfer the time-critical datato the application if the network communication device has not detecteda packet error, and wherein the network communication device is furtherdesigned to communicate to the application that transmission errors haveoccurred and no valid data are available in this transmission cycle ifthe network communication device has detected a packet error.

In a specific design variant, the component is a control device, whichis designed to control at least one tool of the industrial plant as theat least one other component. In accordance with a further specificdesign variant, the component is a control device of a machine, whereinthe control device is designed to control at least one sensor and/oractuator as the at least one other component, or wherein the componentis a control device of a vehicle, wherein the control device is designedto control a power-assisted steering or servo-assisted braking system ofthe vehicle.

At least two of the previously described components can be part of adata network, which also has a cable-bound or wireless transmissionmedium, wherein the at least two components are connected to each othervia the transmission medium, to be able to perform a transmission ofdata in the data network, in which data packets with a predeterminedpacket length are transmitted cyclically between one of the componentsand at least one other component of the machine or industrial plantwithout a repeat transmission of time-critical data of the data packetbeing possible in a transmission cycle.

In the data network a control device may be designed to control at leastone tool of the industrial plant as the other component and/or designedto control at least one sensor and/or actuator as the additionalcomponent, wherein the control device is designed in such a way that thecontrol unit as the central controller can bi-directionally exchangedata packets with each additional component, and wherein each additionalcomponent is designed in such a way that each of the other componentscan only exchange data packets with the central controller.

The object is also achieved by a method for controlling at least onecomponent in a machine or industrial plant according to one embodiment.In the case of the at least one component, a network communicationdevice is provided for controlling a transmission of data in a datanetwork of the machine or industrial plant, in which data packets with apredetermined packet length are transmitted cyclically between thecomponent and at least one other component of the machine or theindustrial plant without a repeat transmission of time-critical data ofthe data packet being possible in a transmission cycle. The methodcomprises the steps: tolerating, with the network communication device,a possible packet error in a received data packet which was sent in thepreceding transmission cycle, determining with the network communicationdevice whether or not the at least one other component has signaled apacket error for a data packet transmitted by the component in thepreceding transmission cycle, adjusting using the network communicationdevice, depending on the determined result, the number of redundancydata items in the data packet to be sent in the following transmissioncycle, which will increase a correction probability of bit errors in thetime-critical data to be sent, and including signaling data in the datapacket to be sent, which signal to the at least one other component apresence or absence of a packet error in the following transmissioncycle.

The method achieves the same benefits as are cited above in relation tothe component.

Further possible implementations of the disclosure also comprisecombinations of features of the embodiments either described previouslyor in the following in relation to the exemplary embodiments, which arenot explicitly mentioned. A person skilled in the art will also be ableto add individual aspects as improvements or additions to each basicform of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the disclosure are presented in the drawings anare explained in more detail in the description below.

In the drawings:

FIG. 1 shows a highly simplified view of an industrial plant, in whichcomponents of the industrial plant according to the first exemplaryembodiment are connected in a data network for performing datatransmission;

FIG. 2 shows a simplified structure of an encoded data packet with weakchannel coding according to the first exemplary embodiment;

FIG. 3 shows a highly simplified structure of an encoded data packetwith strong channel coding according to the first exemplary embodiment;and

FIG. 4 to FIG. 6 show diagrams each illustrating a method forcontrolling a component in an industrial plant according to the firstexemplary embodiment.

DETAILED DESCRIPTION

In all figures, identical or functionally equivalent elements arelabelled with the same reference numeral, unless otherwise indicated.

FIG. 1 shows an industrial plant 1, which can be, for example, aproduction line for vehicles, furniture, building structures, etc., or achemical plant etc., in which media or workpieces 4, 5 are transportedand/or can be processed with at least one tool, such as with anagitator, a welding tool, a screwdriver and/or drill, a stamping tool, ariveting tool, etc. Alternatively, the industrial plant 1 may also be orhave a machine, however, such as a printing machine, a CNC computer(CNC=Computerized Numerical Control), etc., which has at least onecontrolled actuator and/or drive, for example for a controlled pressureroller, etc. The machine is optionally a vehicle, which has a controllerfor a power steering system or servo-assisted braking system or forother components of the vehicle. Any number of other examples of amachine and/or industrial plant 1 are conceivable.

In the specific example of FIG. 1, the industrial plant 1 has a controldevice 10 as a component of the machine or industrial plant 1, atransmission medium 20 and at least one additional component 31, 32, 33.The control device 10 and the at least one additional component 31, 32,33 of the machine or industrial plant 1 use the transmission medium 20jointly and form a data network. Both the control device 10 and the atleast one other component 31, 32, 33 can each bi-directionally exchangedata in the form of data packets 21, 210 via the transmission medium 20for applications 101, 311 to 31N, 321, 331 to 33N. For this purpose, thecontrol device 10 has a network communication device 100.

The at least one other component 31, 32, 33 has one of the networkcommunication devices 310, 320, 330 in each case, as shown in FIG. 1. Inthe transmission medium 20 a fault 25 can occur, which can cause errorsin the transmission of the data packets 21, 210. In the case of anunshielded cable as a transmission medium 20 or in the case of a radiotransmission via the transmission medium 20, such a fault 25 is, forexample, an external radiation as a result of electromagnetic radiation,which is emitted in particular by devices, thunder and lightning storms,etc.

The control device 10 as an application 101 has, for example, amicrocontroller, a storage device, and software, etc. The softwareimplements, for example, a comparison device that compares actualvariables in the operation of the industrial plant 1 with target values.In addition, an evaluation device can be implemented, which on the basisof the output of the comparison device produces new control data, whichare to be transferred in the data packets 21, 210 in real time ornon-real time over the transmission medium 20 to the at least oneadditional component 31, 32, 33. The real-time control data are thengenerally referred to as time-critical data. The non-real-time controldata are generally referred to as non-time-critical data.

The first additional component 31 is, for example, a device which as atleast one application 311 to 31N has at least one element to becontrolled, in particular at least one actuator or drive unit. The atleast one actuator or drive unit can drive an axle into a rotary motionor alternatively into a linear motion. In particular, the firstadditional component 31 can be a robot, a transport device, a rotarymachine, a screw tool, an agitator, etc. The control of the firstadditional component 31 and/or its at least one application 311 to 31Nis performed at least partly on the basis of the control data of thecontrol device 10, which the first additional component 31 receives inthe data packets 21, 210.

The second additional component 32 is, for example, an operating device,which is to be controlled in relation to which displays are displayed byit, or which is controlled by inputs from a user, for example. As anapplication 321, the operating device has, for example, a keyboardand/or a mouse and/or a touch-sensitive or non-touch-sensitive displayscreen etc., or combinations thereof. In particular, the operatingdevice is a control panel, a personal computer, a laptop, a smartphone,tablet PC, etc. The control of the second additional component 32 and/orits at least one application 321 is performed at least partly on thebasis of the control data of the control device 10, which receives thesecond additional component 32 in the data packets 21, 210.

The third additional component 33 is, for example, a sensing device,which has at least one sensor as application 331 to 33N. The at leastone sensor can detect actual values of physical or chemical propertiesof the workpieces 5, 6 or dimensions or distances of tools from theworkpieces 5, 6, etc., according to requirements. Arbitrary types ofactual values are conceivable. The control of the third additionalcomponent 33 and/or its at least one application 331 to 33N is performedat least partly on the basis of the control data of the control device10, which the first additional component 33 receives in the data packets21, 210.

The additional components 31, 32, 33 each transmit data packets 21 ordata packets 210 to the control device 10 as a component of theindustrial plant 1. The data packets 21, 210 contain, for example,results of the control processes, produced in the additional components31, 32, 33 based on the control data of the control device 10. Each datapacket 21, 210 corresponds to one of at least two channel codings of thetransmission medium 20. The at least two channel codings each lead tothe same encoded packet length, as shown in FIG. 2 and FIG. 3.

FIG. 2 shows the structure of a data packet 21 in more detail. The datapacket 21 has four different sections, which are ordered sequentially intime in a predetermined packet length N. The predetermined packet lengthN corresponds to a number of bits N. The data packet 21 has a firstsection for signaling data 211, a second section for time-critical data212, a third section for non-time-critical data 213 and a fourth sectionfor first redundancy data 214. In this case, the first and secondsection together have a number of bits LL The non-time-critical dataitems 213 have a number of bits L2. Therefore, the first redundancy dataitems 214 have a number of bits N-L1-L2. The signaling data 211 containpieces of information 211A, 211B as to whether the precedingtransmission was successful or not, and pieces of information whichspecify the current configuration of the error correction, for examplethe number of check bits, as will be more accurately described andexplained in reference to FIG. 4 to FIG. 6.

In accordance with FIG. 3, in the case of a data packet 210 by contrast,only three different sections are present, which are also are arrangedsequentially in time in the predetermined packet length N. Thepredetermined packet length N corresponds to the number of bits N. Thedata packet 210 also has the first section for signaling data 211 andthe second section for time-critical data 212. However, the data packet210 has a third section for second redundancy data 215. Here again, thefirst and second section together have the number of bits L1. Therefore,the second redundancy data items 215 have a number of bits N-L1.

The data packet 21 according to FIG. 2 corresponds to a weaker channelcoding than the data packet 210 according to FIG. 3. The parameters ofthe channel coding are chosen in such a way that the number of user bitsin the stronger channel coding for the data packet 210 is at least equalto the length of the time-critical data 212. The length of thetime-critical data 212 is derived from the number of bits for thetime-critical data 212.

In the normal case, during operation of the network communicationdevices 100, 310, 320, 330 a moderate channel coding with a relativelysmall number of redundant bits is used. Due to this low level ofredundancy, in addition to transmitting the L1 bits for the signalingdata 211 and the time-critical data 212, it is also possible to transmitL2 bits for non-time-critical data 213. Therefore, in the normal case adata packet 21 is transmitted.

The moderate channel coding in accordance with the data packet 21 ischosen in such a way that, for the expected bit error probability of thetransmission over the transmission medium 20, in most cases alltransmission errors can be eliminated. The packet error probability PER₁does not yet necessarily correspond to the desired error probability ofsystem-critical multiple errors.

The stronger channel coding in accordance with the data packet 21 ischosen in such a way that, despite the higher number of redundant bits,the same coded predefined packet length N is used as in the moderate orweaker channel coding. Therefore, the number of user bits is reduced.This can be achieved in one case by the transmission ofnon-time-critical data 213 being temporarily suspended. Alternatively oradditionally, the transmission of time-critical data 212 that can beomitted at the present time can be suspended, in the hope that they willbe transmitted correctly again in the next cycle. The parameters of thestronger channel coding are chosen in such a way that the probability oferror after the decoding is less than the target probability of thecritical multiple errors.

If in the normal case the weak channel coding is used, hence the datapacket 21 is used, the probability of single packet errors is PER₁. Ifsuch a single error is detected by the control device 10 or one of thecomponents 31, 32, 33, the stronger channel coding is applied in thenext cycle, i.e. a data packet 210 is used. The conditional probabilitythat a first error occurs and a new error then occurs is PER₂. Theprobability of double errors is thus PER₁·PER₂.

In the following, by reference to FIG. 4 to FIG. 6 the communication isdescribed which takes place in the operation of the industrial plant 1between the control device 10 as a component of the industrial plant 1and the other components 31, 32, 33. As a result, a method forcontrolling a component 10, 31, 32, 33 in the machine or industrialplant 1 is carried out. The method can be integrated into any suitabletransmission methods, such as Sercos III, EtherCAT, Profinet, etc.

In FIG. 4 to FIG. 6 the time axis runs from bottom to top. Atransmission cycle K has a duration T_K. A transmission cycle K+1, whichdirectly follows the transmission cycle K, has a duration T_K+1. Thetransmission capacity, which is provided as an example of the periodicor cyclic communication between the control device 10 and the othercomponent 31 in the transmission cycles K and K+1, is represented inFIG. 4 by the rectangles for the packets 21A. In FIG. 5 and FIG. 6packets 21B, 210A are also transmitted, as will be explained below.

In the method, the data to be transmitted, i.e. time-critical andnon-time-critical data 212, 213, are transferred by one of theapplications 101, 311 to 311N to a MAC Layer 1001, 3101 (MAC=MediaAccess Control) in the respective network communication device 100, 310.The MAC layer 1001, 3101 controls how the data packets 21A, 21B, 210Aare assembled depending on the system status. The system status isoriented, for example, according to which tasks are to be performed inthe machine or industrial plant 1.

The respective data packets 21A, 21B, 210A are then transferred to achannel coding/decoding layer 1002, 3102, where depending on thesetting, a weak or strong redundancy is added. This results in thedifferent type of channel coding 200 shown for the data packets 21A,21B, 210A in FIG. 2 and FIG. 3.

As a result, a data packet 21A contains time-critical andnon-time-critical data 212, 213 and redundancy data 214 and in thesignaling data 211 a signal 211A, that the data of a data packet of thepreceding transmission cycle were error-free.

A data packet 21B is structured in the same way as a data packet 21A,except that in the signaling data 211 a signal 211B shows that the dataof a data packet of the preceding transmission cycle were noterror-free, and therefore a packet error 26 (FIG. 5 and FIG. 6) waspresent.

A data packet 210A contains time-critical data 212 and redundancy data214, and in the signaling data 211 a signal 211A that the data of a datapacket of the preceding transmission cycle were error-free.

The coded data packets 21A, 21B, 210A are then transmitted in thetransmission medium 20, wherein only the reserved transmission resource,in particular a specific time slot, can be used. If the fault 25 occursin the transmission medium 20, bit errors can occur in the data packets21A, 21B, 210A during the transmission via the faulty medium 20.

At the network node or the control device 10 or one of the components31, 32, 33, the respective data packet 21A, 21B, 210A is received anddecoded. In most cases any bit errors can be eliminated by the errorcorrection. If this is not possible, transmission errors should at leastbe reliably detected. Known methods are suitable for this, such ascyclic redundancy check (CRC).

There are also possibilities for combined error correction and errordetection, however. The information as to whether the transfer wassuccessful is communicated firstly to the MAC layer 1001, 3101 of thenetwork node or the control device 10 or one of the components 31, 32,33. The MAC layer 1001, 3101 then forwards the received user data,namely the time-critical and/or non-time-critical data 212, 213, to theapplication layer 1001, 3101 or discards erroneous data. Secondly, thenetwork node or control device 10 or one of the components 31, 32, 33transmits the success or failure of the channel decoding by means of thelayer 1002, 3102 together with its user data in the reverse direction.The basic procedure in this case, consisting of assignment of the packetstructure, channel coding, transmission with the assigned resource anddecoding at the receiver, is identical to the forward direction.

The bi-directional communication in the transmission medium 20 can beimplemented, as shown in FIG. 4 to FIG. 6, as a half-duplex procedure,in which transmission can only take place in one direction at any giventime. Alternatively, the bidirectional communication in the transmissionmedium 20 can be implemented as a full-duplex procedure, in which it ispossible to transmit in both directions at the same time. The rest ofthe transmission capacity, which is obtained due to the free time framesbetween the reserved frames, could be used for additional transmissionservices or other network nodes.

FIG. 4 shows a transmission without packet errors for the transmissioncycles K and K+1. Therefore, only the weaker channel coding is used inboth transmission directions. As a result, data packets 21A are sent ineach case. The successful error correction is communicated to the MAClayer 1002, 3102 as message 216A and to the transmitter by the ACKsignal 211A. As long as the control device 10 or the component 31receives an ACK as the signal 211A, the weak channel coding is used forthe following cycle.

By contrast, in the example of FIG. 5 a packet error 26 occurs in theforward direction in the transmission cycle K. If such a packet error 26cannot be corrected in the cycle K during the channel decoding in thenetwork node such as the component 31, but can be detected, then thiswill be communicated to the MAC layer 1002, 3102 as message 216B. TheMAC layer 3102 then discards the received user data 212, 213. The packeterror 26 is communicated to the application layer, which then respondsaccordingly. In the case of the non-time-critical data 213 atransmission retry may be requested. It is assumed that in spite of thepacket error 26 the ACK signal 211A is always received correctly and itis known to the receiver which channel coding 200 was applied in eachcase.

Due to the fact that an ACK signal 211A is received, time-critical data212 and non-time-critical data 213 are transmitted in the reversedirection as usual and protected with the weaker channel coding. It isnow signaled to the control device 10 with the NACK signal 211B that apacket error 26 has occurred in the forward direction. Therefore, thedata packet sent by the component 31 to the control device 10 is now adata packet 21B.

If the control device 10 receives the data packet 21B with the NACKsignal 211B, in the following cycle K+1 it briefly interrupts thetransmission of non-time-critical data 213, and instead uses thestronger channel coding for the next transmission in the forwarddirection. For the resulting data packet 210A with the ACK signal 211A,new packet errors 26 in the time-critical data 210A are then highlyunlikely.

By contrast, FIG. 6 shows an example in which a packet error 26 occursin the transmission cycle K in the reverse direction. The procedure hereis equivalent to packet errors 26 in the forward direction. The packeterror 26 is detected in the control device 10. Therefore, the data error26 is communicated to the component 31 by the NACK signal 211B with thenext data packet 21B in the forward direction in the cycle K+1. Thecomponent 31 in the cycle K+1 then interrupts the transmission ofnon-time-critical data 213 and instead increases the redundancy, so thata data packet 210A is transmitted.

If a transmission error and thus packet error 26 occurs in both theforward and reverse direction directly one after another, then themethod works for as long as the NACK signals 211B can be receivedwithout errors. As a result, in the next cycle the stronger channelcoding is used in both transmission directions and further packet errors26 are avoided.

For the present method, different channel codings 200 are necessary,which each have the same predefined data packet length N, but differentcorrection properties. For such an adaptive channel coding, one of thefollowing options is conceivable depending on requirements:

a) Convolutional codes with different puncturing, such as used in WLAN(WLAN=Wireless Local Area Network).

b) Use of block codes with equal block length for different levels oferror correction performance. It must be noted that both the channelcoding and the channel decoding can change significantly. In thisalternative design two different decoder algorithms must also beimplemented. In the case of a block coding, the volume of information orsignaling bits can be divided into blocks. For each block, redundantcheck bits known as parity bits are added, which can be used to correcta certain number of bit errors. The redundancy of the channel codinghere reduces the user data rate for a given total data rate.

c) Iterative coding methods, in which a plurality of codes is nested. Anexample of this are product codes. Each additional nested code increasesthe error correction properties, but reduces the data rate at the sametime. For the weaker channel coding, the innermost coding and thecorresponding decoding could be omitted. By using this approach, thesame decoder structure can be partly used for both coding variants.

Thus, the adaptive channel coding 200 in the present method does notrelate to an errorful data packet itself, but to the data packetfollowing the errorful data packet. The individual packet error 26 isinitially accepted. The likelihood of recurrence of a packet error 26,however, is reduced due to the stronger channel coding using packets210. The signaling 211B of the first packet error 26 can still takeplace in the first cycle. The additional delay until the followingerror-free data packet is received is only extended by the transmissionof the additional redundancy and the somewhat more complex errorcorrection. This delay is still tolerable by most real-time systems,however, and is much lower than in a method in which it is attempted toretrospectively correct the packet error 26 that has already occurred,without the need to send the entire data packet 21, 210 again. This isbecause such a packet is only available at the receiver error-free aftera delay, which results from the error signaling, transmission of theadditional redundancy and performing the error correction. Such a longdelay is often not compatible with time-critical real-time systems.

In a modification of the present method, it is ensured that for eachtransmission the following two pieces of information are alwaystransferred error-free.

Firstly, it is ensured that the receiver knows unambiguously and withouterror which channel coding 200 is currently being used. This means thatthere is no danger that either a part of the strong redundancy ismistakenly kept for non-time-critical data 213, or thatnon-time-critical data 213 are misinterpreted as part of the strongerredundancy and, as a consequence, time-critical data are wronglycorrected.

Secondly, it is ensured that the receiver can receive the correct signal211A, 211B error-free in each case. If an ACK signal 211A ismisinterpreted as a NACK signal 211B, then the transmission ofnon-time-critical data 213 will be unnecessarily interrupted in order toapply a stronger channel decoding. This reduces the effective user datarate for the non-time-critical data 213 more than necessary. If, on theother hand, a NACK signal 211A is misunderstood as an ACK signal 211A,then despite a first transmission error, the channel coding is notstrengthened. The likelihood of critical multiple errors is therebygreatly increased.

To prevent this, the two pieces of information are optionally secured bya separate strong channel coding, which is independent of the channelcoding 200 of the user data 212 and/or 213 and also has an extremely lowerror probability. Since here only two bits need to be protected, such apermanent, stronger channel coding would be acceptable. The two piecesof information could be included in the signaling data 211.

According to a second exemplary embodiment the control device 10 has theabsolute control over the transmission via the transmission medium 20.In this case, a deterministic behavior applies. Such behavior isstandard practice for a network with a central controller as the controldevice 10 and is common practice in many industrial networks.

Here, the central controller as control device 10 has sole control overthe time-critical resource allocation and the data formats used. In thecase of non-time-critical data 213, in some cases the slaves or theother components 31, 32, 33 can autonomously access the channel of thetransmission medium 20. However, a slave cannot assume it will obtainsole access here.

The sole control over the data format of the time-critical data 212 isalso present in the present method, even if the component 31 in theexample of FIG. 5 instructs the control device 10 as a centralcontroller with the NACK signal 211B to change the packet structure inthe next cycle. It is conceivable though, for the control device 10 as acentral controller to retain the final control over the packet typesused, if this seems to make sense for specific reasons. Thus, thecontrol device 10 as the central controller could ignore NACK-signals211B in the forward direction and continue to use the weaker channelcoding. This makes sense, for example, if no other time-critical data213 are available for transmission. On the other hand, the controldevice 10 as the central controller could also use a stronger channelcoding 200 in the forward direction, despite an ACK-signal 211A in thereverse direction.

The channel coding 200 in the reverse direction could be controlled bythe control device 10 as the central controller by signaling 211A, 211Bof ACK and NACK, regardless of whether the preceding decoding wassuccessful or not. However, the components 31, 32, 33 should not deviatefrom the standard procedure. Thus, they should always apply the channelcoding 200 according to the signaling and report detected errorsuncorrupted to the control device 10 as the central controller.

A third exemplary embodiment is based on the assumption that a minimumof two or more packet errors 26 are critical for the correct operationof the industrial plant 1. In other words, in the case in which M>3consecutive errors are system-critical, the procedure taken is asfollows. The stronger channel coding is only used if M−1 consecutivepacket errors 26 have already occurred. This also results in more leadtime for the network devices 10, 31, 32, 33 for changing the channelcoding. However, when using the stronger channel coding even the firstpacket error leads to a system failure.

According to a fourth exemplary embodiment, for the case in which M>3consecutive packet errors 26 are needed for a system-critical state, thestronger channel coding is used when fewer than M−1 consecutive packeterrors 26 have occurred. This only leads to a system failure if morethan one packet error 26 occurs with stronger channel coding. Thisprobability is significantly lower.

According to a fifth exemplary embodiment, for the case in which onlyM>3 consecutive packet errors 26 are system critical, up to M−1different strengths of channel coding are provided and the channelcoding 200 is increased for each additional consecutive packet error 26.

Depending on the choice of the methods according to the first to fifthexemplary embodiment, a good compromise can always be found between ausable data rate and the avoidance of critical multiple errors.

All previously described embodiments of the system and the methodexecuted thereby can be used individually or in all possiblecombinations. In particular, all features and/or functions of thepreviously described exemplary embodiments can be combined as required.In addition, in particular the following modifications are conceivable.

The parts shown in the figures are illustrated schematically and maydiffer in their exact embodiment from the forms shown in the figures, aslong as their features described above are guaranteed.

The industrial plant 1 can be a programmable logic controller (PLC). Theindustrial plant 1 can be a CNC controller (Computerized NumericalControl). The industrial plant 1 can be or have a movement logiccontroller, for example for transport systems or for guiding tools, etc.

As an alternative to the previously described method, in which the grosspacket length is constant and the net amount of data is briefly reduced,e.g. by suspension of non-time-critical data, it is possible that theamount of user data remains constant and the gross packet length isbriefly increased.

The previously described method may be used in any desiredconfigurations or systems, in which data must be transmitted in atime-critical way, but isolated packet errors are not critical. Theapproach described is particularly interesting for real-timecommunication in industrial automation. But any other real-time datastream is conceivable, in which individual packet errors can still becorrected by interpolation, but multiple errors are to be prevented.Other examples can be control tasks in vehicles (steer-by-wire,brake-by-wire), where it is more important in the event of an error thatcurrent commands are transmitted successfully, than that previouscommands are repeated.

What is claimed is:
 1. A component for one of (i) a machine and (ii) anindustrial plant, the component comprising: a network communicationdevice configured to control a transmission of data in a data network ofthe one of (i) the machine and (ii) the industrial plant, the networkcommunication device being configured to cyclically transmit and receivea plurality of data packets having a predetermined packet length betweenthe component and at least one other component of the one of (i) themachine and (ii) the industrial plant, without a repeat transmission oftime-critical data of the plurality of data packets being possible in atransmission cycle, wherein the network communication device isconfigured to tolerate a possible packet error in a first data packet ofthe plurality of data packets that was received in a precedingtransmission cycle, and to signal to the at least one other component ina following transmission cycle one of (i) a presence and (ii) an absenceof a packet error in the first data packet, wherein the networkcommunication device is configured to determine whether the at least oneother component has signaled a presence of a packet error in a seconddata packet of the plurality of data packets sent by the component inthe preceding transmission cycle, wherein the network communicationdevice is configured to, depending on whether the at least one othercomponent has signaled the presence of a packet error in the second datapacket, increase a number of redundancy data items in a third datapacket of the plurality of data packets to be sent in the followingtransmission cycle to increase a correction probability of bit errors intime-critical data to be sent, wherein the network communication deviceis configured to, if no packet error is determined in the precedingtransmission cycle, one of (i) increase a number of time-critical dataitems in the third data packet to be sent in the following transmissioncycle and (ii) include non-time-critical data, which are to betransferred but for which a time delay is uncritical, in the third datapacket to be sent in the following transmission cycle, and wherein thenetwork communication device is configured to, if a packet error isdetermined in the preceding transmission cycle, include the redundancydata items in the third data packet to be sent in the followingtransmission cycle instead of one of (i) the non-time-critical data and(ii) a portion of the time-critical data.
 2. The component according toclaim 1, wherein the network communication device is configured toinclude in a fourth data packet of the plurality of data packets to besent in a current transmission cycle (i) a first piece of informationindicating whether the first data packet, which was sent from the atleast one other component to the component in the preceding transmissioncycle, had a packet error, and (ii) a second piece of informationindicating the current configuration of the fourth data packet, which isused by the at least one additional component for error correction ofthe time-critical data.
 3. The component according to claim 2, whereinat least one of: the first piece of information consists of one bit andthe second piece of information specifies a number of check bits in thefourth data packet; and the redundancy data items are check bits.
 4. Thecomponent according to claim 2, wherein the network communication deviceis configured to (i) examine the time-critical data for bit errors and,(ii) if at least one bit error is present, perform an error correctionof the time-critical data based on the second piece of information andthe redundancy data.
 5. The component according to claim 1, furthercomprising: an application configured to use the time-critical data,wherein the network communication device is configured to transfer thetime-critical data to the application in response to the networkcommunication device not detecting a packet error, and wherein thenetwork communication device is configured to inform the applicationthat transmission errors have occurred and that no valid data areavailable in a current transmission cycle in response to the networkcommunication device detecting a packet error.
 6. The componentaccording to claim 1, wherein the component is a control device, andwherein one of: the at least one other component is at least one tool ofthe industrial plant and the control device is configured to control theat least one tool; the at least one other component is at least one of asensor and an actuator of the machine and the control device isconfigured to control the least one of the sensor and the actuator; andthe at least one other component is one of a power-assisted steeringsystem and a servo-assisted braking system of a vehicle and the controldevice is configured to control the one of the power-assisted steeringsystem and the servo-assisted braking system.
 7. A data network for oneof (i) a machine and (ii) an industrial plant, having a transmissionmedium, the transmission medium being one of cable-bound and wireless,and at least two components connected to each other via the transmissionmedium, each of the at least two components comprising: a networkcommunication device configured to control a transmission of data in thedata network of the one of (i) the machine and (ii) the industrialplant, the network communication device being configured to cyclicallytransmit and receive a plurality of data packets having a predeterminedpacket length between the respective component of the least twocomponents and at least one other of the least two components, without arepeat transmission of time-critical data of the plurality of datapackets being possible in a transmission cycle, wherein the networkcommunication device is configured to tolerate a possible packet errorin a first data packet of the plurality of data packets that wasreceived in a preceding transmission cycle, and to signal to the atleast one other component in a following transmission cycle one of (i) apresence and (ii) an absence of a packet error in the first data packet,wherein the network communication device is configured to determinewhether the at least one other of the least two components has signaleda presence of a packet error in a second data packet of the plurality ofdata packets sent by the component in the preceding transmission cycle,wherein the network communication device is configured to, depending onwhether the at least one other of the least two components has signaledthe presence of a packet error in the second data packet, increase anumber of redundancy data items in a third data packet of the pluralityof data packets to be sent in the following transmission cycle toincrease a correction probability of bit errors in time-critical data tobe sent, and wherein the network communication device is configured toinclude in a fourth data packet of the plurality of data packets to besent in a current transmission cycle (i) a first piece of informationindicating whether the first data packet, which was sent from the atleast one other component to the component in the preceding transmissioncycle, had a packet error, and (ii) a second piece of informationindicating the current configuration of the fourth data packet, which isused by the at least one additional component for error correction ofthe time-critical data.
 8. The data network according to claim 7,wherein: one of the at least two components is a control device; atleast one other of the least two components is at least one of (i) atleast one tool of the industrial plant, and (ii) at least one of asensor and an actuator of the machine and the control device isconfigured to control the at least one other of the least twocomponents; the control device is configured as a central controller tobi-directionally exchange data packets with each additional component ofthe least two components; and each additional component of the least twocomponents is configured to only exchange data packets with the centralcontroller.
 9. A method for controlling a component for one of (i) amachine and (ii) an industrial plant, the component having a networkcommunication device configured to control a transmission of data in adata network of the one of (i) the machine and (ii) the industrialplant, the network communication device being configured to cyclicallytransmit and receive a plurality of data packets having a predeterminedpacket length between the component and at least one other component ofthe one of (i) the machine and (ii) the industrial plant, without arepeat transmission of time-critical data of the plurality of datapackets being possible in a transmission cycle, the method comprising:tolerating, with the network communication device, a possible packeterror in a first data packet of the plurality of data packets that wasreceived in a preceding transmission cycle, determining, with thenetwork communication device, whether the at least one other componenthas signaled a presence of a packet error in a second data packet of theplurality of data packets sent by the component in the precedingtransmission cycle, adjusting, with the network communication device,depending on whether the at least one other component has signaled thepresence of a packet error in the second data packet, a number ofredundancy data items in a third data packet of the plurality of datapackets to be sent in the following transmission cycle to increase acorrection probability of bit errors in time-critical data to be sent,and including signaling data in the third data packet that signals tothe at least one other component one of (i) a presence and (ii) anabsence of a packet error in the first data packet.